In fluids that are recovered from ground reservoirs, such as from residential or commercial wells, the fluids may contain objectionable impurities, such as radon or Volatile Organic Chemicals (VOC's). Radon, which is a colorless, odorless, radioactive gas produced from the natural decay of uranium, is naturally emitted from the ground or found in well water. Outdoors, radon is naturally diluted and is not typically thought of as a health hazard, whereas when trapped in a closed environment or in water (or some other fluid) in sufficiently high concentrations, it is considered to be deleterious to health. In fact, several epidemiological studies have identified radon as a potent carcinogen that causes lung cancer in human beings. It has been estimated that between 500 to 1500 lung cancer deaths annually are due to radon contamination of residential potable water supplies. Moreover, the risk from water contaminated with radon is actually considered to be higher than the combined risk from all of the other man-made chemical contaminants that may be found in residential drinking water.
In order to solve this problem, systems have been developed to remove these impurities and unfortunately these radon removal systems are typically complicated and relatively expensive to install and maintain. There are currently three (3) known methods for treating fluids contaminated with radon gas to remove the gas; decay storage, Granular Activated Carbon (GAC) filtration and spray aeration. Decay storage simply involves storing water in a large water tank for a period of time to allow the radon contained therein to naturally dissipate. This is possible because radon has a radiological half life of only 3.785 days and as such, allowing the water to sit for a period of time, such as a month, greatly reduces the amount of radon contained in the water by approximately 99.5%. Unfortunately however, decay storage requires a large tank which includes a device to maintain essentially plug flow conditions to prevent back mixing. Additionally, although GAC filtration systems are somewhat effective, radioactivity can build up in the adsorbent filter bed. This adsorbent filter bed gives off radioactivity in the form of gamma rays (primarily) as the radon decays and may itself present a health hazard. Another disadvantage to GAC filtration systems involves the disposal of the radioactive GAC filter when it becomes contaminated with other water borne impurities, such as iron, sediment and/or bacteria.
Aeration systems, on the other hand, are also effective, but they do not accumulate radioactivity. The aeration method involves introducing air into the water supply to increase the gas-liquid interface, thereby allowing the radon gas contained in the water to diffuse into an air/radon gas mixture which is then vented from the water supply into the outside atmosphere. Unfortunately, although current aeration system configurations allow for the removal of a limited amount of radon from the water, they tend to include a pump to achieve the aeration effect. Thus, they tend to be very noisy and increase electricity consumption.